Lunar Scientists Evaluate Apollo 11's Contributions

When Neil Armstrong and Buzz Aldin stepped onto the fine, loose soil of the lunar surface 20 years ago next week, science had a number of questions to ask of the moon. Was it geologically hot, or was it cold? What was its origin? Were there any protobiological substances on its surface? What geologic differentiation had occurred in its formation? How did it differ from the earth? What were the mascons, those mysterious subsurface objects, that perturbed the orbits of lunar satellites? Now, as NASA celebrates Apollo 11 with a series of events and parties in Houston and Cape Canaveral, where does lunar science stand? Among planetary astronomers there’s a consensus that the Apollo program was a scientific success. At the same time, their theories about the moon’s origin and composition await the proof of new physical evidence—evidence that lunar scientists believe only another moon mission could acquire. The 841 pounds of rock that the Apollo 11 astronauts and 10 later visitors to the moon brought back has been carefully examined, and most of it has been stored for the rise of later generations of scientists. About 100 pounds of it has been probed rigorously; during the past two decades, scientists have sliced it, weighed it, measured it, photographed it in a multitude of lights, shot it with high-energy particles, and planted seeds in it. The results show that the mascons, once the darlings of speculation, are unusually dense regions where lava once pooled. The discovery that molten rock played a major role in the moon’s evolution is one of the major finds of the Apollo program. Contrary to informed thought before Apollo 11—most prominently the informed thought of the late Harold C. Urey, who at the time was professor-at-large of chemistry at the University of California, San Diego—the moon appears to have a hot, geologically active history, not to mention a pretty warm present. Perhaps most important for lunar scientists, the Apollo rocks give them a basic chronology of events. Before the landings, some astronomers believed that large-scale cratering on the moon happened often and had taken place as recently as 20,000 yeas ago. Now, says planetary scientist George Weatherill, who directs the Department of Terrestrial Magnetism at the Carnegie lnstitution of Washington, “the evidence is that the last 3 billion years have been relatively consistent”—and quiet, with no major impacts. But the big question—the moon’s origin—is still up for grabs. The Apollo findings enoouraged the “magma ocean” theory of lunar evolution, which pictured a largely molten new moon, independently formed. Current thought, sparked in part by evidence that the lunar surface is depleted of heavier metals, favors a radically different approach to lunar origin, suggesting that the spoon was formed when a Mars-sized body struck the earth. Few scientists expect to prove either theory until another close exploration of the lunar surface. 67 Laboratories Even though, as Weatherill says, “The cream has been taken off the top of the lunar rock collection,” there’s still work to be done on the samples. Indeed, nothing’s been done to most of them except cataloging. Of the 841 pounds of rock brought back by the Apollo missions, about 617 pounds have never left the Johnson Space Center in Houston. Fifty-seven pounds have been examined rigorously, and either returned to the space center or destroyed in experimentation. A little more than 117 pounds are in "dead storage” at Brooks Air Force Base in San Antonio, Texas. The remaining 50 pounds are distributed around the world—to museums, to friendly heads of state, and, at this moment, to 67 laboratories. James Arnold, a former principal investigator of the lunar rock who now holds a professor of chemistry chair named for Urey at UCSD, belongs to a peer committee called the Lunar and Planetary Sample Team, 2 which every year reviews between 00 and 300 proposals for experiments on the rocks and decides who gets what and how many fractions of a gram they’ll get. Arnold himself has submitted an ambitious proposal for 10 grams, for his studies of the loose surface regolith and its record of radiation bombardment. The National Aeronautics and Space Administration does its own research on the lunar samples, but its budget for lunar science, remaining constant for the last 15 years at about $7 million, has been eaten away by inflation. The Lunar Receiving Laboratory, Building 37 at the Johnson Space Center, which quarantined the first lunar astronauts and their samples to protect the earth from contamination, is now used by NASA primarily for medical work. The samples are next door, in Building 31, and the quarantine, enforced by bank-like vaults and pressured chambers, has been reversed, to protect the rocks from being contaminated by the terrestrial environment. Mike Duke, a former principal investigator of the samples who now watches over them as head of NASA’s Solar Systern Exploration Division, says the bulk of the material is kept untouched so that “as we improve our technology we can lean things from samples we haven’t worked with before.” Some scientists look back at the Apollo period with nostalgia. John Wood, now at the Harvard Smithsonian Center for Astrophysics in Cambridge, Mass., had been a meteorite researcher until, like many of his colleagues, he became involved with lunar analysis. He has since returned to meteorite studies. With about an ounce of borrowed lunar material still in his office safe, Wood says of his Apollo years: “It was wild and romantic, and we were learning so much. I told myself, ‘Wood, this is going to be the high point of your life,’ and it was.” However, Wood has kept his hand in: He’ll help analyze the radar images from the Magellan Venus probe. Not all lunar scientists need lunar rock. Earth-based observers, not yet passed have gone to the infrared to learn more shout the moon’s makeup, while other astronomers work to tie down transient events like the apparent outgassing photographed by Greek astronomers in 1985. Recent spectroscopic observa tion of the central mountain in Copernicus revealed evidence of dunite, material thought to have come from the mantle during the impact that formed the crater. Talk to a lunar scientist nowadays, and he or she will tell you that great science was along with the Apollo samples, and more great science awaits our return to the moon. Weatherill notes that the Apollo landings missed several geologically diverse regions. Arnold suggests that ice could be found in the shadows of craters at the moon’s poles. Larry Haskin, former head of NASA’s Planetary and Earth Sciences Division, is experimenting at Washington University in St. Louis with ways to turn lunar rock into resources that would make space travel cheaper and easier. The fulfillment of these scientists’ wish for a return to the lunar surface remains distant. On the drawing boards since the mid-1970s, however, is an unmanned satellite that would orbit the moon frqm pole to pole. NASA spokesman Charles Redrnond, calling the Polar Orbiting Lunar Observer (POLO) “a high-priority science mission,” is optimistic that Congress will provide startup funding for the project by fiscal 1992, making a launch possible by 1995. Before that, perhaps as early as 1992, the first-ever privately owned research spacecraft, the Lunar Polar Probe, could be launched by the Space Studies Institute, a Princeton, NJ.-based nonprofit organization. Equipped with a gamma-ray package, the satellite would search for lunar ice, paving the way for the POLO flight. Lunar-orbiting satellites may not be the next giant leap for mankind, but for lunar scientists it’s a great next step. After settling for spacecraft observations confined to the areas near the lunar equator during the Apollo era, POLO scientists will now get high-resolution spectral mapping of the entire surface. If ice is found at the poles, it could make a lunar base cheaper—and more feasible. Most lunar scientists believe that human habitation of the moon is inevitable, and so is the return to earth of more moon rocks. After all, the moon has plenty left.

Lunar Scientists Evaluate Apollo 11's Contributions

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Ken Kalfus

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July 1989

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